Under auspices of the Project on Human Development in Chicago Neighborhoods, 6,000 males and females, having the initial ages 1, 4, 7, 10, 13, and 16, and residing in 80 neighborhoods in Chicago will be assessed, along with their caregivers, in annual home-based sessions over a 4 year period. These six age groups constitute separate overlapping cohorts which will be studied simultaneously in a single longitudinal design. The assessments of these children will ascertain the source, frequency, and severity of their exposure to violence and the consequences of such exposure for subsequent psychiatric disorder, social, psychological, physiological, and academic functioning. An important feature of the longitudinal cohort design is that it is embedded in a community study of the social organization of neighborhoods, schools and families that has yielded multi-level, multi-method measures of ambient violence within each of these social contexts. The consolidation of longitudinal and community designs is the product of several years of advance work by an interdisciplinary group of researchers in which theoretically derived measures of neighborhood social organization have been achieved, the analytic methods for studying multi-level, longitudinal designs developed and tested, and a comprehensive protocol for measuring individual and family level risk factors composed and piloted. The aims of the study are of both a descriptive and analytic nature. The descriptive goals are to determine the prevalence and correlates of exposure to violence and PTSD in the context of a large urban environment varying markedly in the social class and ethnic group compositions of its neighborhoods. The analytic aims relate to an examination of the causal links between exposure to violence and PTSD and other psychiatric disorders, as well as to an investigation of the consequences of such exposure for the cognitive, social, and academic functioning of children. To augment this population-level analysis, a detailed assessment will be conducted of a subsample characterized by exposure to either acute or chronic violence. The focus of this effort will be on understanding the role that adrenal regulation of stress, as reflected in salivary levels of cortisol, plays in mediating the consequences of traumatic experiences. The study promises to advance current understanding of the causes and prevention of PTSD in children and to improve the planning and efficacy of health promotion and violence prevention activities at the local community level.